1. Field of the Invention
The field of art to which this invention relates is printers, in particular, an envelope leveler for a high volume printer having a top-feeder in which envelopes are fed into the printer.
2. Description of the Related Art
In printers of the prior art, particularly those which employ a top-feeder for storing and feeding a top envelope from a stack of envelopes into the printer, the envelope stack presents a problem in that the top envelope is not properly oriented for feeding into the printer. The improper orientation of the top envelope of the envelope stack is due to the tendency of a stack of envelopes to be higher at one side then the other side.
A typical printer 100 of the prior art having such a top-feeder paper feed arrangement is shown in FIG. 1. The top-feeder 102 generally includes a paper tray 103 and employs a pick roller 104 for contacting and feeding the top envelope 106 from the top of the envelope stack 108 into the printer 100. A gearbox and motor assembly 110 drive the pinch roller as necessary to feed the top envelope 106. Since the height of the envelope stack is uneven, as is shown in FIG. 1, the pick roller 104, which is generally located in the center of the envelope stack along a central axis C--C, does not efficiently engage and feed the top envelope 106 into the printer 100.
Furthermore, since the top envelope 106 is skewed with respect to the pick roller 104, one of its ends 108a is elevated over the other end 108b, causing the top envelope 106 to rotate while feeding into the printer 100, resulting in improper feeding and a subsequent paper jam.
Devices are known in the prior art to account for the uneven height of an envelope stack which is to be fed into a printer. While these devices have their advantages, they are generally complex and costly, such as that disclosed in U.S. Pat. No. 5,520,381 to Lo et al. Their complexity and cost also make them difficult, if not impossible, to retrofit onto existing printers. The prior art devices also do not account for a varying degree of unevenness in an envelope stack.
Another prior art solution to the problem has been to manipulate the envelopes themselves to eliminate the unevenness in the height of the envelope stack. U.S. Pat. No. 4,807,805 to Rutkowski creates an assembly of two envelopes of uniform thickness that can be torn apart after printing. U.S. Pat. No. 4,915,288 to Kao et al. adds a flat sheet of adhesive to the individual envelopes of an envelope stack to make them a uniform thickness. U.S. Pat. No. 5,755,433 to Klein prints on flat unfolded sheets which are folded into envelopes after printing.
For these reasons an envelope leveler is needed which is simple, inexpensive, easy to retrofit onto existing printers and accounts for the degree of unevenness in a stack of envelopes to be fed into a printer, particularly one which employs a top-feeder system.